The objective of this proposal is to understand the molecular basis for the biological functioning of porphyrin systems. There are four principal parts to the project, listed in the order in which progress has been made: (1) Study of the optical absorption and luminescence spectra and theoretical study of the electronic energy levels of exotic metal porphyrins, with the aim of understanding clearly the relation of d to pi energy levels and their relation to redox; (2) study of vapor deposited porphyrins films to determine absorption and emission sectra, conductivity, and photoconductivity with the aim of using these materials for the direct conversion of photon energy to electrical energy based on biological analog; (3) synthesis and study of iron porphyrins with fifth and sixth histidine ligands covalently linked to the porphyrin through side chains, to study their redox properties, binding of ligands, and electronic spectra; (4) synthesis and study of covalently linked double porphyrins and chlorins containing different metals and study of energy transfer and electron transfer between these molecules and to acceptor molecules in solution after flash excitation.